Javad Behmanesh; Nasrin Azad Talatape
Volume 19, Issue 51 , April 2015, , Pages 41-58
Abstract
One of the atmospheric cycle properties is climatic changes which can cause the fluctuations in meteorological parameters. These fluctuations in many world regions are considerable and water and soil resources are affected by them. To prepare against undesirable effect of climate change and adopt suitable ...
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One of the atmospheric cycle properties is climatic changes which can cause the fluctuations in meteorological parameters. These fluctuations in many world regions are considerable and water and soil resources are affected by them. To prepare against undesirable effect of climate change and adopt suitable development programs and water resources management, it is necessary to investigate the meteorological variable changes. The objective of this research was to investigate the climate change in Urmia region. In this research, the changes trend of temperature, precipitation, relative humidity, sunshine and potential evapotranspiration were studied. To achieve this goal, Urmia synoptic station daily data with 40 years period (1971-2010) were used. The Mann-kendall statistical test at confidence level of 95% was used to investigate the significance of trend in the mentioned parameters. The results showed that the trend slope of maximum, minimum and average of temperature was positive and this trend in 95% confidence level was significant. Urmia precipitation was decreased with slope of -2.26 so that this decrease was significant. The sunshine had positive slope and significant trend, but the negative trend of relative humidity and the positive trend of potential evapotranspiration (0.0068) were not significant. The monthly investigations showed that the average temperature in all months had positive slope, but this slope was not significant in all months. The other parameters in some months had positive or negative slopes.
Saeed Jahanbakhsh; Majid Rezaee Banafshe; Marziyeh Esmaeelpour; Masoomeh Tadayoni
Volume 16, Issue 40 , September 2012, , Pages 25-46
Abstract
Accurate estimating of potential evapotranspiration is essential for many studies related to agriculture and water balance. This study was carried out with the aim of surveying models for estimating potential evapotranspiration in the southern basin of Aras river. For this purpose, the monthly data of ...
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Accurate estimating of potential evapotranspiration is essential for many studies related to agriculture and water balance. This study was carried out with the aim of surveying models for estimating potential evapotranspiration in the southern basin of Aras river. For this purpose, the monthly data of 6 stations including mean air temperature, minimum and maximum temperature, wind speed, sunshine hours, mean and minimum relative humidity were used in the statistical period of 20 years (1986-2005).
After reconstruction missing values and controlling stations for being reference (well irrigated) or non reference, potential evapotranspiration values were computed applying 9 methods (FAO- Penman- Monteith, Blanney-Criddle, Hargreaves-Samani, Makkink, Turc, ASCE standardized method, Kimberly- Penman, Penman and Priestly-Taylor) in REF-ET software. For determining best method, calculated potential evapotranspiration values were compared with evaporation pan values by using correlation coefficient and root mean square difference. Results indicated that there was significant correlation between Blanney-Criddle and pan evaporation values. Therefore, Blanney-Criddle model was selected as the best model for the study area. Afterwards, based on the above mentioned model and also the use of interpolation technique, the potential iso-evapotranspiration map was drawn for the southern basin of the ArasRiver.
